Lecture 1

• Shoot system:

  • Above ground
  • Stem, leaves, flowers, fruits
  • Role: absorb sunlight, gas exchange, reproduction
• Root system:

  • Below ground
  • Role: anchor plant, absorb water &nutrients, store energy, symbiotic relationships (fungi, bacteria)
• Tap root – eudicot plants

  Fibrous roots – monocot plants

  Phenotypic plasticity – grow deeper in drier soil
• Leaves:

  Large surface area maximizes light capture

  Small surface area minimizes water loss
• The plant cell:

  Middle lamella - pectin glues cells together to form tissues & organs

  Primary wall – created first; made of cellulose; resists internal pressure; allows plants to stay upright & prevents cells from lysing

  Secondary wall – only in specialized cells (xylem); thick & made of cellulose & lignin (cross-linked polyphenols); provides strength; important for water transport (esp. in trees)

  Simple pits – thin areas of secondary wall that connect adjacent cells
• Amylase breaks alpha 1-4 glycosidic bonds
• Some animals have symbiotic relationships with microbes that can digest cellulose

  Monogastric herbivores have symbiotic gut bacteria

  Ruminants have a 4-chambered stomach that includes anaerobic bacterial digestion of cellulose

  Termites have symbiotic relationship with gut bacteria & protozoa
• Plant vs. animal cell

  1. Plants have cell wall made of cellulose

  2. Plants have chloroplast (not all plant cells)

  3. Plant cells are generally larger than animal cells

  4. Plant cell is rectangular or cubic, animal is round or irregular

  5. Animal cells contain centrioles, higher order plants do not

  6. Animal cells contain intermediate filaments, plant cells do not

  7. Plants cells have 1 large vacuole, animals have many small ones

  8. Animal cells have more mitochondria – higher energy requirement 

  9. Plant cells have plasmodesmata, animal cells do not
• Plants: microtubules form spindle fibres without centrosomes/centrioles
• Modified roots:

  Anchor roots - stems to walls and other plants

  Prop roots - adventitious, stabilizes the stem

  Pneumatophores - allow gas exchange between roots and atmosphere

  Storage roots - stores carbs and nutrients in tap roots
• Modified shoots:

  Water storage - stems store water (cactus)

  Stolons - produces new individuals horizontally at nodes above ground

  Rhizomes - produces new individuals horizontally at nodes below ground

  Tubers - underground stem stores carbs (potatoes)

  Thorns - protection from herbivores
• Modified Leaves:

  • Bulbs - stores food (edible part of onion)
  • Succulents - stores water (aloe vera)
  • Tendrils - aid in climbing (pea leaves wrap around)
  • Floral mimics - attract pollinators
  • Traps - traps insects to digest them with enzymes or bacteria
• Plastids: A small organelle found in plant cells that contains chloroplasts.

  Chloroplast in leaves - photosynthesis and gas exchange

  Amyloplast in roots - carb storage

  Chromoplast - synthesis and storage of carotenoid pigments so that insects are attracted for pollination